Airplane kite

ABSTRACT

A tethered airplane kite design comprising a planar fuselage, a horizontal stabilizer, a vertical stabilizer, one or more pairs of wing members oppositely disposed and connected to the fuselage, and a string attachment point located directly below and in the same plane as the fuselage. All wing members incorporate sweep back and a positive dihedral. The horizontal stabilizer is at a negative angle of attack of approximately 13* with respect to the main wings. The rigid air frame structure and the position of the point to which the tether is attached with respect to the aerodynamic characteristics of the wing structure provide for an exceedingly stable flight characteristic.

United States Patent 1 Stratton Sept. 11, 1973 I AIRPLANE KITE [76] Inventor: Craig A. Stratton, 12821 Martha Ann Drive, Los Alamitos, Calif. 90720 [22} Filed: Sept. 24, 1971 21 Appl. No.: 183,543

52 U.S. Cl. 244/154 [51] Int. C1. B64c 31/06 [58] Field of Search 244/154, 153 R, 153 A, 244/155 R, DIG. 1; 46/76-81.

[56] References Cited UNITED STATES PATENTS 3,412,964 11/1968 Johnson 244/153 R 2,035,730 3/1936 Trevor 244/154 2,969,946 1/1961 Andrews 244/154 2,124,992 7/1938 Wood 244/154 2,507,777 5/1950 Frey 244/153 R 3,194,520 7/1965 Kurkjian 244/153 R Primary Examiner--Milton Buchler Assistant Examiner-Paul E. Sauberer Attorney-Donald D. Jeffery [S 7 ABSTRACT A tethered airplane kite design comprising a planar fuselage, a horizontal stabilizer, a vertical stabilizer, one or more pairs of wing members oppositely disposed and connected to the fuselage, and a string attachment point located directly below and in the same plane as the fuselage. All wing members incorporate sweep back and a positive dihedral. The horizontal stabilizer is at a negative angle of attack of approximately 13 with respect to the main wings. The rigid air frame structure and the position of the point to which the tether is attached with respect to the aerodynamic characteristics of the wing structure provide for an exceedingly stable flight characteristic.

9 Claims, 4 Drawing Figures PATENTEU SEN 1 I975 SHEEI 1 BF 2 CRAIG A. STRATTON Pmmsnsmmn I 3,758,057

SHEET 2 BF 2 mvENToR. CRAIG A. STRATTON BACKGROUND OF THE INVENTION 1. Field of Invention I This invention relates generally to a tethered, aerodynamically sustained craft and more particularly to an airplane kite which embodies, first an improved wing structure wherein only the leading, center, and outer edges are fixed and the fabric wing surface is allowed to billow and determine its own angle of attack in order to match flight conditions and, second, an airframe which promotes directional stability.

Although the present invention finds particularly advantageous application in the field of toy kites; and although, in the cause of brevity, most of the following discussion and description of examples of the invention relate thereto, it is to be understood that the advantages of the invention are manifest equally as well to other fields of tethered aerodynamic flight, such as, for example, military reconnaissance kites, rescue markers, and radio or radar targets, beacons, relays, antennae or the like.

2. Description of the Prior Art It is an objective of most tethered kite designs to develop a large lift to drag ratio and to produce maximum dynamic stability during varying wind conditions. It has been found in the past, that certain airplane kite designs can achieve a lift to drag ratio greater than that for the conventional and well known diamond kite design. As a trade off, however, these prior art airplane and in their assembled relationship whereby they provide an exceedingly durable and flexible structure.

In accomplishing these and'other objects of this invention, I have provided the improved details of construction, the preferred embodiments of which are illustrated in the accompanying drawings, wherein BRIEF DESCRIPTION OF THE DRAWINGS leading edges and the free trailing edges which develop kite designs generally sacrifice dynamic stability and simple construction for the greater lift to drag ratio.

In a patent issued to E. A. Founds, U.S. Pat. No. 1,620,882 a biplane kite design is described wherein an attempt was made to develop an auxiliary, variable wing surface. This design in addition to being delicate and complicated for knockdown, simple assembly, does not develop the same dynamic stability because the angle of attack does not vary as in the instant invention.

Another biplane kite of more, recent design is described in a patent to A. H. Trevor, U.S. Pat. No. 2,035,730. This patent attempts to develop a variable angle of attach wing by means of manually adjustable swivel wings.

SUMMARY OF THE INVENTION I This invention solves the aforementioned problems by utilizing a free trailing edge wing design, which, in combination with the other design features, especially the fixed but flexible leading edge, sweepbackdihedral of the wings, and a relatively negative angleof attack of the horizontal stabilizer, creates a dynamically stable kite with an effective lift to drag ratio of from three to eight.

Accordingly, it is an object of this inventionto provide a tethered, aerodynamically sustained craftwhich has a high lift to drag ratio and is stable under varying wind conditions.

, It is also an object .of this invention to provide a kite construction that is exceedingly light in weight; that is substantial and durable in use; that is inexpensiveto manufacture, that employs relatively few parts, and is adapted to be made and shipped knocked down for subsequent assembly.

Other objects of the invention reside in the details of construction of the various parts, in their combination,

a cambered aerodynamic wing profile and a billowing arch in the trailing edge during flight.

FIG. 3 is a frontal view of a biplane kite showing the dihedral of the upper and lower wings, a horizontal stabilizer approximately 13 negative with respect to the main wings and the consequent camber and billowing arch of the trailing edge developed by the free or unattached trailing edge of all wing surfaces.

FIG. 4 is an isolated perspective view of an alternate wing structure for use in a kite representing a jet plane wherein each wing includes two spars, one of which forms the leading edge of the main part of the wing which has a free trailing edge, and! the other forms the leading edge for a plurality of superimposed leading edge slats which facilitate greater lift at higher angles of attack for the wing.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring more particularly to FIG. 1, the airplane kite l hereinafter described in its preferred embodiment is in general construction a miniature representation of the well known French Nieuport 28 biplane of World War I.

The airplane kite l is comprised of a longitudinally extending fuselage section 2, a horizontal stabilizer 3, a vertical stabilizer 4, a wing support frame integral with the fuselage 5, a pair of upper wing members, 6 and 7, and a pair of lower wing members, 8 and 9 respectively, both pairs of which emanate from and are oppositely disposed to said support frame 5. Although the preferred embodiment describes two pairs of oppositely disposed wing members, the invention contemplates a single pair or a plurality of oppositely disposed wing members from the uppermost pair to the lowermost pair of wing members.

The fuselage section 2 as shown in FIG. 1 is a triangular shaped planar member which provides a strong keel effect for longitudinal stability. Said fuselage includes a pair of lightweight ribs 10 and 11 which join one another at the rearward end 12 and are separated by the main strength member 13 of the wing housing frame at the forward end. The nose of the fuselage is a profile representation of the engine cowling, coplanar with the fuselage, and made up of sheet balsa wood 14, rib sticks 15 and paper covering 16. Trussing ribs such as 17 and 18 are located within the triangular fuselage for dimensional stability. The rib members are typically made of the initial angle of attack of each wing and in this preferred embodiment the lower wing has about 3 to 4 more angle of attack than the upper wing. Also the main strength member 13 is built into the fuselage in such a way that the lower wing is set to the rear of the upper wing. The remaining frame members 21, 22, 23, 24, and 25 add necessary strength and rigidity to the fuselage and wing housing frame. The fuselage section 2 is covered with a lightweight flexible material such as paper or cloth. 1

Although the preferred embodiment describes a planar fuselage, this is not critical. Other shapes such as cylindrical, rectangular and trapezoidal would also suffice. Similarly, the structure need not be skeletal in construction. A light weight, rigid fuselage of expanded cellular formaceous material would be suitable.

Inasmuch as all wing members embody the same structure, a detailed description, FIG. 2, of only upper wing member 6 follows.

Upper wing member 7 includes a leading edge single spar 26, a wing tip chord 27, and a cross brace 28 all made of spruce wood or some other suitable material with similar mechanical properties. The wing area material is made of a light, flexible material such as paper or cloth which does not permanently become stretched during stresses of normal flight. The trailing edge 29 is left free to billow as necessary during flight thereby forming a cambered wing profile shape in the fore and aft direction and billowing arch of the trailing edge. The cambered profile has been found to greatly enhance lift and permits a lift to drag ratio in the range of 68 under optimum wind conditions. The conventional diamond shaped kite usually operates with a lift to drag ratio of about 1.

Optimum flight characteristics have been obtained wherein the fixed leading spar 26 defines wing sweepback in the range of 040, usually about 10, and a positive dihedral of 5-30. These pre-set angles are assured in the preferred embodiment by using channel blocks 30 as shown in FIGS. 1 and 2 which connect the fixed leading spar with the main strength member of the wing housing frame.

The rearward portion of the fuselage 2 includes a vertical stabilizer 4 which is defined by the triangular area formed between rib 10 and vertical stabilizer rib 31. Similarly, a horizontal stabilizer 3 is formed by a pair of oppositely disposed spars 32 and 33 which emanate rearwardly from fuselage rib 11 at an angle approximately 13 negative with respect to the fixed leading edge spans of the upper and lower wing members and ribs 19 and 20. The area of both the vertical and horizontal stabilizers 4 and 3, respectively, is covered with a suitable lightweight material such as paper, cloth, or plastic. Similarly, the trailing edges 34 and 35 of both the tail and horizontal stabilzer respectively, are left free. The negative angle of attack of the horizontal stabilizer with respect to the upper and lower wing members assists in maintaining anose-up attitude which ensures good lift during tethered flight and, should the tether break, prevents the kite from assuming a glide attitude by causing repeated stalls and in this way facilitates the kites recovery within a short distance.

The airplane kite in flight is controlled by a line 36 which is connected at an attachment point 37 lying in the same plane as the fuselage and almost directly below and a little forward of the cummulative center of lift of the wings. Said attachment is formed by the intersection of downwardly extending ribs 38 and 39 which integrally communicate with the lower fuselage rib 11 and also visually represent the landing gear of the airplane.

ALTERNATE WING EMBODIMENT includes a plurality of superimposed leading edge slots 48. These slots are created by affixing small wing surfaces, 49, to the fixed leading edge spar 43, wing tip chord 44, central chord 41, and the short engine mounting chords 50. The trailing edges of these slots, 51, do not extend back as far as the forward edge of the main wing spar, 42, and are free to billow. The slots extend rearward no more than one fourth of the total length of the central chord, 41, or wing tip chord 44 pieces. These slots increase the lift characteristics of the wing. The profile shapes, 52, are strictly for decoration and are meant to represent the engines of a jet plane.

I claim:

1. An airplane kite comprising a. a longitudinally extending fuselage;

b. a tethering means;

0. a pair of wing frame members emanating from and oppositely disposed to said longitudinally extending fuselage, wherein said wing frame members include a fixed and flexible leading edge, a fixed central wing root chord piece integral with and extending in length for a portion only of said fuselage and a fixed wing tip chord piece, wherein said frame members are substantially rectangular in constructron; 1

d. a flexible wing covering material attached to said frame members thus developing substantially rectangular wings having free trailing edges wherein said wings permit an automatically adjustable angle of attack; and

e. a horizontal stabilizer wherein said stabilizer maintains a negative angle of attack with respect to said pair of wing members.

2. An airplane kite according to claim 1 furtherincluding a vertical stabilizer emanating from a rearward portion of said longitudinally extending fuselage section.

3. An airplane kite according to claim 2 wherein said longitudinally extending fuselage and said vertical stabilizer are coplanar,-and wherein said tethering means includes a guideline attached to a connecting point located directly below and in the same plane as said longitudinally extending fuselage.

4. An airplane kite according to claim 2 wherein said wing frame members further include a second superimposed wing covering of lesser overall dimension than said first wing covering, wherein said second wing covering is attached to said leading edge, and further includes a second free trailing edge.

5. An airplane kite according to claim 1 wherein said wing frame members have a sweepback angle and a positive dihedral.

6. An airplane kite according to claim 5 wherein said wing frame members incorporate a sweepback angle of from -'40 and wherein said wing frame members incorporate a positive dihedral of from -30, and wherein said horizontal stabilizer maintains a negative angle of attack of approximately 0-20 with respect to said wing members. I

7. An airplane kite comprising a. a longitudinally extending fuselage;

b. a tethering means;

0. a plurality of pairs of wing frame members emanating from and oppositely disposed to said longitudinally extending fuselage, wherein said wing frame members include a fixed and flexible leading edge,

a fixed central wing root chord piece integral with and extending in length for a portion only of said fuselage and a fixed wing tip chord piece, wherein said frame members are substantially rectangular in construction; I

d. a flexible wing covering material attached to said frame members thus developing substantially rectangular wings having free trailing edges wherein said wings permit an automatically adjustable angle of attack; and

e. a horizontal stabilizer wherein said stabilizer maintains a negative angleof attack with respect to said pair of wing members.

8. An airplane kite according to claim 7 wherein said plurality of pairs of wing frame members maintain the same relative aspect ratio, and wherein the relative size of each pair of wing frame members decreases from a largest uppermost pair to a smallest lowermost pair.

9. An airplane kite comprising a. a planar longitudinally extending fuselage section; b. a tethering means; a c. a vertical stabilizer coplanar with said fuselage section emanating from a rearward portion of said fuselage; d. two parallel pairs of wing members oppositely disposed to said longitudinally extending fuselage section and emanating therefrom, wherein an upper pair of said wing members is larger in overall dimension than a lower pair of said wing members, wherein each of said wing members is of substantially rectangular construction and has the same aspect ratio, a positive sweepback angle of from l020, a positive dihedral angle of from l0-20, a fixed leading edge, a fixed central wing root chord, a fixed outer wing tip chord, a flexible wing covering material attached thereto and a free, trailing edge, wherein said wing members permit an automatically adjustable angle of attack, and a horizontal stabilizer emanating from said fuselage section where said stabilizer is at a negative angle of attack with respect to said main wings. 

1. An airplane kite comprising a. a longitudinally extending fuselage; b. a tethering means; c. a pair of wing frame members emanating from and oppositely disposed to said longitudinally extending fuselage, wherein said wing frame members include a fixed and flexible leading edge, a fixed central wing root chord piece integral with and extending in length for a portion only of said fuselage and a fixed wing tip chord piece, wherein said frame members are substantially rectangular in construction; d. a flexible wing covering material attached to said frame members thus developing substantially rectangular wings having free trailing edges wherein said wings permit an automatically adjustable angle of attack; and e. a horizontal stabilizer wherein said stabilizer maintains a negative angle of attack with respect to said pair of wing members.
 2. An airplane kite according to claim 1 further including a vertical stabilizer emanating from a rearward portion of said longitudinally extending fuselage section.
 3. An airplane kite according to claim 2 wherein said longitudinally extending fuselage and said vertical stabilizer are coplanar, and wherein said tethering means includes a guideline attached to a connecting point located directly below and in the same plane as said longitudinally extending fuselage.
 4. An airplane kite according to claim 2 wherein said wing frame members further include a second superimposed wing covering of lesser overall dimension than said first wing covering, wherein said second wing covering is attached to said leading edge, and further includes a second free trailing edge.
 5. An airplane kite according to claim 1 wherein said wing frame members have a sweepback angle and a positive dihedral.
 6. An airplane kite according to claim 5 wherein said wing frame members incorporate a sweepback angle of from 0*-40* and wherein said wing frame members incorporate a positive dihedral of from 5*-30*, and wherein said horizontal stabilizer maintains a negative angle of attack of approximately 0*-20* with respect to said wing members.
 7. An airplane kite comprising a. a longitudinally extending fuselage; b. a tethering means; c. a plurality of pairs of wing frame members emanating from and oppositely disposed to said longitudinally extending fuselage, wherein said wing frame members include a fixed and flexible leading edge, a fixed central wing root chord piece integral with and extending in length for a portion only of said fuselage and a fixed wing tip chord piece, wherein said frame members are substantially rectangular in construction; d. a flexible wing covering material attached to said frame members thus developing substantially rectangular wings having free trailing edges wherein said wings permit an automatically adjustable angle of attack; and e. a horizontal stabilizer wherein said stabilizer maintains a negative angle of attack with respect to said pair of wing members.
 8. An airplane kite according to claim 7 wherein said plurality of pairs of wing frame members maintain the same relative aspect ratio, and wherein the relative size of each pair of wing frame members decreases from a largest uppermost pair to a smallest lowermost pair.
 9. An airplane kite comprising a. a planar longitudinally extending fuselage section; b. a tethering means; c. a vertical stabilizer coplanar with said fuselage section emanating from a rearward portion of said fuselage; d. two parallel pairs of wing members oppositely disposed to said longitudinally extending fuselage section and emanating therefrom, wherein an upper pair of said wing members is larger in overall dimension than a lower pair of said wing members, wherein each of said wing members is of substantially rectangular construction and has the same aspect ratio, a positive sweepback angle of from 10*-20*, a positive dihedral angle of from 10*-20*, a fixed leading edge, a fixed central wing root chord, a fixed outer wing tip chord, a flexible wing covering material attached thereto and a free, trailing edge, wherein said wing members permit an automatically adjustable angle of attack, and a horizontal stabilizer emanating from said fuselage section where said stabilizer is at a negative angle of attack with respect to said main wings. 